Do migrant birds have more pointed wings?: A comparative study

Summary Do birds that migrate over longer distances have more pointed wings than more sedentary birds? Within several bird genera, species differ considerably in their migration distances. This makes it possible to study the extent to which different taxa show similar morphological solutions to common selection pressures. I selected 14 species, two from each of seven passerine genera, to maximize within-genus differences in migration distance. Wing lengths and the lengths of eight primary feathers around the wing tip were measured to assess wing length and shape. Primary lengths were transformed to take into account the allometric relationship between the length of each feather and wing length and then collapsed into summary measures of shape by principal component analysis. I used the method of independent contrasts to address the effects of phylogeny. Wing length showed no relationship with migration distance. There was a correlation between migration distance and wing shape. It is concluded that long-distance migration has resulted in convergent morphological evolution of long distal and short proximal primaries, resulting in wing tips close to the leading edge of the wing.     

Glucose starvation stimulon of Escherichia coli: role of integration host factor in starvation survival and growth phase-dependent protein synthesis.

The DNA-binding protein IHF was found to be required for starvation survival and for the induction of 14 proteins of the glucose starvation stimulon. Many of these proteins have been shown previously to be general responders to diverse stress conditions. Overexpression of IHF during balanced growth was not sufficient to induce these proteins, but it resulted in an increased synthesis of rpoH-dependent heat shock proteins.     

Some notes on the ecology of a GermanBranchipus schaefferi population (Crustacea: Anostraca)

Habitat preference, seasonal occurrence, starvation resistance, hatching eggs ofBranchipus schaefferi, and effects of predation onB. schaefferi were studied.Branchipus was only present in turbid, unvegetated ponds and absent in ponds which contain higher aquatic vegetation and theSpirogyra sp. The first individuals ofB. schaefferi appeared in April when water temperature was 10 °C and the last adults in November at a water temperature of 3.5 °C. Up to 6 reproducing generations were observed during this period. Abundance ofB. schaefferi was higher in temporary ponds than in permanent ponds. Sex ratio was close to unity for most of the year. Body size ofB. schaefferi males and females was significantly positively correlated with pond volume. Without foodB. schaefferi could survive for 1.5 to 2 days at 20 °C and 4 to 5 days at 10 °C. Hatching success of eggs decreased when eggs were dried for 7 months. Freezing of eggs had no effect on hatching success. From] the predators tested,Chaoborus sp. larvae clearly selected smallB. schaefferi; one consumed approximately 6Branchipus d–1 at a density of 6 to 12 prey 1–1. The other predators, dragonfly larvae, and larvae and adults ofTriturus alpestris selected alternative prey types, for exampleTubifex sp. and ostracods.     

Genetic relationships among species of hagfish revealed by protein electrophoresis

Hagfish species of the genera Myxine, Eptatretus and Paramyxine were analysed for genetic variation by allozyme electrophoresis and isoelectric focusing of general proteins. Large genetic differences were observed between samples of supposed conspecifics of Myxine circifrons from off the Californian coast, and also within one sample of Paramyxine sp. from Sagami Bay, Japan. The results are convincing evidence of the existence of additional sympatric species in these two areas. In general, the highest genetic identities were found between species within the subfamilies Myxininae and Eptatretinae. Within Eptatretinae, the Japanese species Eptatretus burgeri was genetically more similar to Japanese species of Paramyxine than to American species of Eptatretus . Thus, our data indicate that the generic status of Paramyxine should be reconsidered.     

Kinetic model of disaccharide oxidation by Agrobacterium tumefaciens

Disaccharides were microbaially transformed to their corresponding 3-keto-derivatives by resting cells of Agrobacterium tumefaciens NCPPB 396. The kinetics and yield of this highly specific oxidation depend on several factors. The oxygen concentration especially has a major influence on the production of 3-keto-derivatives and was investigated kinetically with respect to low stationary oxygen concentrations in solution. Experiments showed unconventional results that conflicted with normal Michaelis-Menten kinetics. A kinetic model was developed and the kinetic constants were calculated. The model and experimental data for sucrose, maltose, iso-maltulose (palatinose), and leucrose are in good agreement with each other. Initial reaction rates with different sugars using constant oxygen concentrations resulted in a Michaelis-Mentent type function. The complete kinetics, including the effect of disaccharide and oxygen concentrations, are presented. (c) 1995 John Wiley & Sons, Inc.     

Purification of monoclonal antibodies from whole hybridoma fermentation broth by fluidized bed adsorption

To achive the coarse purification of a monoclonal antibody from whole hybridoma fermentation broth a fluidized bed cation exchange process was used. The procedure consisted of application of the crude sample and washing of the bed in a fluidized mode and elution in a fixed bed mode. A completely clarified eluate was obtained with purification factors between 4 and 8 and a concentration of the desired product (monoclonal antibody) by a factor of more than 3 was achived. Thus, a combination of the three early steps of the downstream process clarification, concentration and coarse purification was possible. Two different materials were tested: a commercially available agarose-based matrix (Stream-line-SP), and a self-derivatized material based on controlled-pore glass (Bioran). Initial experiments were performed to describe the fluidization of the glass material. Comparison with the agarose material showed several differences, the agarose matrix allowing liquid flow closer to plug flow than the glass material. Increased backmixing in the liquid phase was detected when fluidizing the glass adsorbent compared with the agarose-based matrix. Despite this fact, comparison of the two materials with respect to antibody binding and elution demonstrated a similar performance. (c) 1995 John Wiley & Sons, Inc.     

Mesoderm-specific B104 expression in the Drosophila embryo is mediated by internal cis-acting elements of the transposon

The Drosophila melanogaster genome contains about 100 copies of the B104 transposable element, which is strongly expressed during embryogenesis. Here we show that B104 expression is restricted to the esophageal and amnioproctodeal regions of the embryo and to the developing mesoderm. Mesoderm-specific B104 expression requires the activity of the mesoderm-determining factors twist and snail. Virtually the same expression patterns were observed in Drosophila yakuba, a species that a separated from D. melanogaster by some 15 million years of evolution. We show that B104 expression is directed by internal sequences of the retrotransposon that are capable of acting as a cis-acting regulatory element in front of a heterologous Drosophila promoter. Our findings suggest that retrotransposon insertions can affect the expression patterns of endogenous genes by adding and distributing specific cis-acting control elements throughout the host genome. We therefore propose that transposable elements in addition to reducing the fitness of their hosts may also provide a rich pool of cis-acting sequences that contribute to the long-term evolutionary potential of the population in a beneficial manner.     

Enzyme activity measurements on isolated organs of Brachionus plicatilis (Rotifera)

A method is described by which the integument of Brachionus plicatilis, together with its intracellular lamina, is quickly dissolved before other parts or tissues of the animal are destroyed. After removing the integument several parts of the body can be separated and fractionated in a more or less intact state by centrifugation in a Percoll gradient. The measurement of enzyme activities has indicated that this procedure might provide a way of localizing enzymes within the rotifer body.     

Effects of magnesium and iron on lipid peroxidation in cultured hepatocytes

In primary cultures of rat hepatocytes, the effects of extracellular Mg²⁺ and Fe on lipid peroxidation (LPO) as measured by means of malondialdehyde (MDA) formation were investigated.Incubation of hepatocytes at decreasing extracellular Mg²⁺ concentration enhanced LPO, depending on extracellular Fe. About 96% of MDA accumulated in the culture medium. Addition of desferrioxamine prevented LPO.Additionally, the formation of oxygen free radicals was determined by fluorescence reduction of cis-parinaric acid. With this method, an immediate decay of fluorescence was found after addition of Fe²⁺. Fluorescence reduction was completely prevented by desferrioxamine, indicating the function of extracellular Fe. This mechanism may operate additionally to the increase in intracellular Fe and intracellular formation of oxygen free radicals during Mg deficiencyin vivo.     

Alterations of β-adrenoceptor-G-protein-regulated adenylyl cyclase in heart failure

Alterations of receptor-G-protein-regulated adenylyl cyclase activity have been suggested to represent an important alteration leading to contractile dysfunction in the failing human heart. Recent experiments suggest that the ₁-adrenoceptor(₁AR) density and mRNA levels are reduced, while ₂-adrenoceptors and stimulatory G-proteins are unchanged (mRNA and protein level). Functional assays demonstrated that the catalyst of the adenylyl cyclase is not different between failing and nonfailing myocardium. Inhibitory G-proteins are increased (pertussis toxin substrates, protein and mRNA) and correlate to the reduced inotropic effects of -adrenoceptor agonists and of CAMP-PDE inhibitors. Gi-coupled m-cholinoceptors and A₁-adrenergic receptors are unchanged in density and affinity. Stimulation of these receptors resulted in an unchanged antiadrenergic effect on force of contraction. In conclusion, a downregulation of ₁-AR and an increase of Gi have been observed as signal transduction alteration in failing human myocardium. These alterations are due to alterations of gene expression in the failing heart and are related to a defective regulation of force of contraction in heart failure.